Common end closures for beer and beverage containers have a central panel that has a frangible panel (sometimes called a “tear panel,” “opening panel,” or “pour panel”) defined by a score formed on the outer surface, the “consumer side,” of the end closure. Popular “ecology” can ends are designed to provide a way of opening the end by fracturing the scored metal of the panel, while not allowing separation of any parts of the end. For example, the most common such beverage container end has a tear panel that is retained to the end by a non-scored hinge region joining the tear panel to the reminder of the end, with a rivet to attach a leverage tab provided for opening the tear panel. This type of container end, typically called a “stay-on-tab” (“SOT”) end has a tear panel that is defined by an incomplete circular-shaped score, with the non-scored segment serving as the retaining fragment of metal at the hinge-line of the displacement of the tear panel.
The container is typically a drawn and ironed metal can, usually constructed from a thin plate of aluminum. End closures for such containers are also typically constructed from a cut-edge of thin plate of aluminum or steel, formed into a blank end, and manufactured into a finished end by a process often referred to as end conversion. These ends are formed in the process of first forming a cut-edge of thin metal, forming a blank end from the cut-edge, and converting the blank into an end closure which may be seamed onto a container. Although not presently a popular alternative, such containers and/or ends may be constructed of plastic material, with similar construction of non-detachable parts provided for openability.
These types of “stay-on-tab” ecology container ends have been used for many years, with a retained tab and a tear panel of various different shapes and sizes. Throughout the use of such ends, manufacturers have sought to save the expense of the metal by down-gauging the metal of the ends and the tabs. However, because ends are used for containers with pressurized contents and are sometimes subject to pasteurization, there are conditions causing great stresses to the components of the end during pasteurization, transit and during opening by a user. These conditions limit the available gauge reduction of the end metal, and make it difficult to alter design characteristics of the end, such as by reducing metal gauge or the thickness of the metal residual in the score defiling the tear panel.
The pressurized contents of the container often causes the end to buckle. The pressurized contents will also force the tabs upwardly. There is a maximum allowable distance that the tab can be displaced without the tab extending upwardly above the remainder of the container. This is called tab-over-chime. Tab-over-chime leads to ship abuse problems wherein the frangible panel prematurely fractures during distribution of filled beverage containers.
As manufacturers reduce the thickness of the metal used to make the ends, buckle and tab-over-chime become more and more of a problem. Therefore, a need for can end with improved ability to withstand buckle and tab-over-chime is needed.